Diffuse Optical Imaging Of Brain Function Under Repetitive Transcranial Magnetic Stimulation And In Children With Cerebral Palsy
Dhamne, Sameer C.
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Diffuse Optical Imaging (DOI) is a non-invasive neuroimaging technique which measures the changes in oxy- and deoxy-hemoglobin concentrations at a high temporal resolution based on the principle of Near-Infrared Spectroscopy.DOI was combined with repetitive Transcranial Magnetic Stimulation (rTMS) to assess the neuronal changes induced in the cortical regions, which are directly under rTMS and the connected areas, by applying 1Hz rTMS to the left hemisphere of the motor cortex followed by the stimulation to the prefrontal cortex for two visits. The DOI signals were simultaneously acquired from both ipsilateral and contralateral brain regions before, during, and after rTMS. We observed that there was no significant difference in the temporal responses between visit 1 and visit 2. Stimulation of both the cortices resulted in a significant decrease in oxy-hemoglobin concentration in both the ipsilateral and contralateral sides, which showed high temporal consistency. Also functional connectivity between the stimulated site (at the selected seed region) and the contralateral regions was investigated by performing a correlation analysis of the DOI time series using seed-region correlation mapping. The correlation maps exhibited a remarkable degree of temporal synchronization between the two hemispheres in both motor and prefrontal cortex, confirming that rTMS generated strong inter-hemispheric effects during and after rTMS.In another clinical study, DOI and Electromyography (EMG) were employed together to assess the cortical activity and reorganization in children affected with Cerebral Palsy (CP), a motor impairment. The results showed that the functional connectivity patterns along with EMG responses for a finger-tapping protocol differentiate the brain activity in healthy and CP children. Finally in a pilot study, the feasibility of a simultaneous functional MRI (fMRI) and DOI approach was tested to validate the DOI results with fMRI yielding high consistency between the two.